Agile makes an important point.

No more electric whine of starter motor spinning compressor.
No more ticking of injectors.
No more batmobile like "whoosh" as the turbine lights.
And no more sweet smell of Jet-A1 that is so redolent of flight, like the sun through Perspex on sheepskin seat covers on a hot day, or the solid feeling of a pair of David Clarks as you clamp them on and adjust the boom mic...


It'll probably sound like a bloody bus, and smell like one too...:{

Yes that sounded like poetry to my ears, like a good wine, its not the drinking its the divine experience of the sense.


but think about it now:
the roar of a pure breed racing engine, those titanium rod moving in perfect unison, those twin turbo spinning to fury speed in 1/4 second and getting into a deep purple glow. the whole thing started by one of these F1 starter, that you find on the Lamborghini Aventador.


By the way that engine use kerosene, so the smell jet fuel stays.

Also consider that the recip diesel engine requires a friction clutch to allow the engine to start and then slip enough to bring the rotor up to speed. This is something a free-power-turbine turboshaft engine does not require.

Centrifugal clutch akin to the Alouette II,


http://www.alouettelama.com/types/318-20.jpg


from left to right: rotor brake, free wheel, centrifugal clutch

WHO says no more JP1 smell?

You can bet on, that this thing runs on JP1...
[NO ONE would install the infrastructure to supply DIESEL for a few ec120D operators - JP1 is aready there..]

3top

Again, I bet there will be no Ec120D and no EC120D operators. This is a demonstrator solely built to draw public funds. I can't imagine this going anywhere.
Best case scenario the engine development will be used in a different aircraft, probably fixed wing.

I agree AH has better things to do than concentrate on small aircrafts (EC120D) when they now have tons of capital and assets to sell EC225s and other high cost ships to the militaries of the world .


Regardless the demonstrator shows that it is possible to have a 5 seat piston helicopter without compromises (either look or performance).


In the best case Guimbal (maker of the Cabri G2) should inherit that technology and make a cool next generation aircraft around it. You know Guimbal has been a protégé of Eurocopter in a sense, and adopted a great part of the EC120 technology concepts (rotor head, avionics presentation, fenestron...)


Why EC did let it happen and even fostered it, I assumed they knew it was not attacking the piece of the pie they care about or would care about in the future. They could have strategized in a sense that it was better to have a known quantity fill that market hole.

Best case scenario the engine development will be used in a different aircraft, probably fixed wing.

Yep and they could call that a........ hmmmnnn... let me think now....

A Diamond!

Possibly because Bruno along with AH actually holds the patents for a lot of those technologies?

The G2 prototype first flew 23 years ago!

The HCE recip diesel H120 flight demonstrator was only intended to validate the analytical modeling work done under the CleanSky Green Rotorcraft program within a reasonable cost. If cost were no object, the entire propulsion system could have been retrofit with a more fully optimized design. Regardless, the finished H120 flight demonstrator is still a very nice piece of work.

While a V8 recip turbodiesel engine using machined aluminum heads/block/crankcase, titanium conrods, etc might seem expensive, in reality a production version of this engine would probably still cost 30-40% less than a similar turboshaft. The recip engine would also have far lower operating costs. This was the focus of much of the analysis modeling work performed by Cranfield University under this project. Here is an excellent technical presentation describing their work (the recip diesel configuration is the "HCE class"): http://www.aerodays2015.com/wp-conte...s-Pachidis.pdf

The recip diesel drivetrain makes economic sense for certain applications as described in the paper above. There are no technical hurdles preventing it from becoming a reality. The only issue is the significant financial commitment required to turn it into a marketable product. There are only a couple aircraft OEMs (like AH) that have the massive financial resources required to complete this type of commercial project.

good presentation, the methodology in there seems to follow like what the airline industry is doing (optimizing flight path for fuel, noise impact...).


if its a sign of things to come, that means no more buzzing the beach at 500ft AGL on a beautiful day. the computer will tell you your finely optimized and most appropriate flight trajectory.


one more point, piston engine have much more torque, than turbines. does that plays any benefit anywhere, for example during training exercise, the instructor can wait a bit more before recovering that sagging RPM that the student mishandled.


is it really that expensive to re engineer the engine part of an aircraft compared to the initial design cost of a program like the EC120.

One good bit of innovation that came out of this is the use of a torsion shaft to drive the main gearbox. Much better than the traditional rubber bands used by other reciprocating engined ships.

Agile- that's a good question.

The Arrius 2F has an output shaft 100% speed of 6000rpm, so at an MCP of 432shp that works out to a torque of 378ft-lb at the MGB input. If we assume the AE440 diesel has a 100% crank speed of 4000rpm, at a similar MCP of 432bhp that works out to a torque of 567ft-lb at the crank. But the diesel engine uses an intermediate gearbox to step the speed up to 6000rpm at the MGB input, so the (mean) shaft torque at this point would essentially be the same as the turboshaft engine.

It's not that the recip diesel has "more torque" than the turboshaft. Instead the big difference between the turboshaft and turbodiesel engines is that the turbodiesel would have far quicker throttle response. The speed of the Arrius 2F gas generator (Ng) is 54,117rpm at 100%, and the rate Ng speed can be changed is limited by combustion stability. So it can take a while for it to spool up from say 85% Ng to 100% Ng in response to increased power demand.

Riff: Thanks! - the ever ongoing confusion with regards to torque, power and rpm... There are gearboxes, you can always have whatever torque you want :)

Thanks for the precision, at operating speed torque is the same. it is as you mentioned the combustion stability that prevents turbines to provide has much punch as the turbo diesel.


if I am not mistaking former design turbine (like the Turbomeca Artouste) used to be quite stable due to a generous dispensing of fuel,
the new generation(like the Arrius 2F) have been starved in the name of fuel economy thus making their operating position/region very small.


those of you who have flown the 300 (not equipped with governor) might know how responsive the engine is on the up side to recover that RPM, (that is, if not over-pitched yet).


I have heard an Arrius 2F cost $475K to overhaul, that tell me engine cost must be a bit above that number, that leaves a lot of money on the table for that turbo diesel engine.

...if you are down to 85% MRrpm and you are NOT in an autorotation and trying to stretch your glide - you are seriously in deep!!

....you are WAY overpitched and no matter the type of powerplant, unless you nearly floor the collective, rpm recovery will NOT be fast, piston or turbine.
[IF you unload the rotor, piston or turbine will recover fast!]

IF you get to 85% under power, it means you asked for more than the powerplant CAN give you, so it is long past (...or actually BELOW) torque levels it can sustain or recover from (without substantially lowering the collective)....

3top:cool:

why is it not possible to have an aviation piston engine that is based on modern technology? :ugh:


an engine that was not designed in 1947 (Lycoming O-540):yuk:
an engine that does not sound like starting a truck (R44):(
an engine that has more than 25KW per liter:ouch:


magnetos!? before coming to aviation I thought only lawnmower used them.


it is really a case where the mainstream solution (ie: turbines) got all the technology focus (dual FADEC and so on ...)


I am not saying turbines are bad, they are ideally fitted for helicopters, but there is a vacuum between the R44 and the H125 that could be filled with a new generation piston engine.


somebody said if we had pursued electric cars 20-30 years ago, they would perfectly adapted now. instead combustion engine cars are perfectly adapted.

Agile- Unless I misread your post, the AE440 diesel engine seems to be exactly that. In fact, with regards to your KW/L metric the AE440 displaces 4.6L and produces 322KW, which works out to almost 70KW/L.

Heck, the AE440 diesel even uses a pair of single stage centrifugal air compressors, each one coupled to its own single stage radial inflow gas turbine. They just call them turbochargers.:ok: If you listen closely when the engine is operating under load, you can probably still hear some of that "sweet turbine whine".

One other very nice thing about a recip turbodiesel that I do not recall hearing mentioned is that it does not have a susceptibility to damage from debris/dust/sand ingestion that a turbine engine does. Perfect for operating in desert environments.

I seriously doubt that. Sand is not healthy for any kind of engine (except maybe silane fuelled engines).

A ( not so ) new generation engine is the ' Rotary Wankel'. Mazda is presently working on a Diesel version and is determined to -once again - win the 24 hours Le Mans race. Subject engine could be a candidate for helicopters and fixed - wings.